ASB 194 LECTURE 5new.doc


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LECTURE 5: SUBSISTENCE PATTERNS AND DIET CHOICE Natural selection acts to favor the most efficient variants in a population that is competing for limited resources. Since organisms need energy (nutrients) to survive and reproduce, natural selection should favor variants that acquire food most efficiently. More resources are converted into more genetic copies thus human brains are designed to desire efficient resource acquisition . The theory developed to explain variation in diet choice and subsistence strategies in simple economies is called Optimal Foraging Theory (OFT) . OFT is similar to economic modeling based on utility maximization in complex societies. This suggests that humans may have a universal evolved tendency to choose economic alternatives that give greatest gain with the least effort . This mini-max principle is believed by many anthropologists to characterize only modern capitalist societies, however empirical evidence suggests that members of all cultures seek to obtain maximum gain from their effort. No society ever described is indifferent to gains from work effort! Ache hunter-gatherers live in the forests of South America. Each day members of an Ache camp wake up, eat breakfast, and then begin searching for food. During the day they pass many edible items and yet stop to acquire only a few of these. Indeed biological inventories show that the Ache forests contain over 100 species of mammals, over 300 species of birds, about 100 species of fish, and several dozen edible amphibians and reptiles. The environment also contains over 30 species of edible insects, over 30 species of edible fruit, and a variety of other edible resources such as palm hearts, roots, and nuts. Nevertheless about 80% of the food in the Ache diet comes from only 8 species of vertebrate prey. The remainder of the diet is composed to a large extent from only 3 species of insects or their honey, one type of palm, and a few minor fruits. The Ache often pass by and ignore edible resources during their food quest. Is this just “cultural preference” or is there another explanation? Slides (all by K. Hill) Ache foragers walking, Hunting, Cebus monkeys, Buchu larva, Kurilla fruit. Palm fiber starch Small guyra taa bird --ignored One model from Optimal Foraging Theory, (called the fine-grained prey choice model), suggests an answer to why the Ache select the resources that they do. The model is based on the same logic as modern economic theory, that people generally attempt to maximize their resource gain rate whenever acquire
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resources (whether food or dollars). The purpose of the model is to help us understand how humans make decisions about which food items to acquire among the many that are available in the environment. Here is an analogous example that is simpler for most Anthropology 101
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This note was uploaded on 03/01/2011 for the course ASB 194 taught by Professor Hill during the Spring '11 term at ASU.

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